1. Field of the Invention
The present invention relates generally to a drill and a method for using the same. More particularly, a design of drills for drillign reinforced concrete, rock or the like and a drilling method for using the same is proposed.
2. Description of the Related Art
Diamond core bits are generally known for drilling the above types of materials. Such diamond bits usually have an adapter connected to and rotating integrally with a drive shaft of an electric motor, a cylindrical body attached to the tip of the adapter, and an annular bit attached to the tip of the body. A multiplicity of diamond segments are fixed to the tip surface of the bit. There is also a type wherein the body and the bit are integrally formed. The diamond core bits having the foregoing designs can drill a desired portion of, by way of example, a reinforced concrete building and can cut a deep hole therein.
However, when a deep hole is to be made into a concrete building or the like with the foregoing diamond core bit, debris due to drilling remains around the diamond segments and increases the drilling resistance. As a result, the drilling efficiency of the diamond core bit deteriorates.
In order to solve the above problem, double cylinder type drills have been proposed. The double cylinder type drill has a body comprised of a shank and a sleeve fixed to the shank. In this type of the drill, compressed air is supplied to a passage formed between the shank and the sleeve. The compressed air is sprayed upon the debris, which is then sucked and discharged through the inside of the drill by means of an aspirator.
In the foregoing double cylinder type drill, the passage for the compressed air must be provided at the adapter and between the shank and the sleeve. However, the shape and the location of the passages in conventional double cylinder type drill tend to be inefficient and make the sleeve difficult to assemble. Therefore, conventional double cylindrical type drills require a long and complicated manufacturing process which leads to high production costs.
When the foregoing double cylindrical type drill is at work and comes into contact with a reinforcing bar for instance, there is also another problem that the self-sharpening effect of the drill bit deteriorates. The self-sharpening effect here means as follows. When abrasive grains forming the diamond segments are abraded, a higher drilling resistance comes about upon the abrasive grains. Thus, a part of the abrasive grains is broken due to the increased resistance. However, the broken part has sharpness and can work as an effective cutting edge. It is called the self sharpening effect. When the self sharpneing effect is lowered, it takes an extended time to drill and cut the reinforcing bars. In some cases, it may become impossible to drill them.